NEW YORK (Reuters Health) - Peanut allergy has proven to be a tough nut to crack. While there's still no way to make peanuts completely safe for people who are allergic to them, an experimental therapy may make them less deadly, report researchers from Germany and the US.

While the research holds hope for the hundreds of thousands of American kids who are allergic to peanuts, there's a lot more research to do before the therapy is ready for "prime time," Dr. Wayne Shreffler, an investigator on the study, told Reuters Health.

Unlike other food allergies -- which might disappear as kids grow up or respond to doctor-supervised "challenges" allowing a child to build up a tolerance to the food -- a peanut allergy usually lasts a lifetime, Shreffler and colleagues note in the Journal of Allergy and Clinical Immunology. And the severity of reactions may vary widely; one accidental exposure may lead to a minor rash, the next could be fatal.

The research team, from Berlin's University Hospital Charite and Mount Sinai Medical Center in New York, wanted to know if a therapy could be developed that was safe to take by mouth and would reduce the threat of accidental peanut ingestion in peanut-allergic kids.

"These patients were carefully selected to have an extremely low probability of growing out of their peanut allergy," said Shreffler, who now practices at Massachusetts General Hospital in Boston.

In the study, the first of its kind, tiny amounts of crushed peanuts were given by mouth to build up tolerance to peanut proteins. To limit the danger of a fatal reaction, the 23 children enrolled in the study were admitted to the hospital for the first week of therapy.

It took an average of 7 months of increasing doses for the kids to work up tolerance to one kernel's worth of crushed peanut or 500 milligrams, more than is usually eaten in an "accidental ingestion," the investigators say. After they reached 500 mg and were able to consume it daily without side effects for 8 weeks, they took two weeks off and then faced a new peanut food challenge.

Before this time, however, more than a third of the kids (35 percent) dropped out of the study, a rate "quite high compared to other studies," the investigators note. Allergic reactions ranging from upset stomach to wheezing were common in all the children. Four, or 17 percent, dropped out because of a bad allergic reaction, a higher adverse reaction rate than some previous work. One patient quit during the hospital phase because of anxiety. Two, including the youngest participant, who couldn't stomach the taste of the peanut/applesauce concoction, were dropped because they wouldn't follow the trial rules.

Fourteen children made it to the end of the study. At the final food challenge, all but two of them were able to tolerate 1 gram of peanut compared to .19 gram at the beginning of the study, leading the investigators to conclude that "some patients" might benefit from this approach known as "oral immunotherapy."

"The glass is half full," Shreffler said. The therapy was able to increase tolerance levels in "many more than would have had any change on their own," he said while urging caution.

Whether the protection lasts longer than two weeks is not answered yet.

"There's evidence there may have been a permanent shift, but we haven't proven that yet. We've only taken the first step," Shreffler said.

The Food and Drug Administration does not regulate therapies such as this and Shreffler urges patients to be wary of anyone offering it.

"There's nothing regulatory to prevent Johnny allergist from starting to give crushed up peanuts to patients in the office," he said.

If a pill is developed, the FDA would become involved.

"That's the best hope. It could be in a pill form or it could be a well defined protocol," Shreffler said, but a good understanding of what's safe and who would benefit is at least five years away.

Clinical trials are underway testing other therapies too, he said, but in the meantime, total avoidance of peanuts and keeping an EPI pen on hand for an emergency injection in case of accidental ingestion, are the only sure ways to protect against a fatal reaction.

According to U.S. government figures, peanuts and tree nut allergies are the leading causes of fatal and near fatal food-allergic reactions.